Pathogenesis of calcium oxalate stones is under study. Serum PTH and 1,25 (OH)2D3 and nephrogenous cyclic AMP are being measured along with response to low calcium diet and thiazide in patients with idiopathic hypercalciuria. Urine saturation and crystal growth inhibition are being measured in stone formers, in response to various forms of treatment. The factors that influence the ability of crystallization to occur on the surface of the urothelium, specifically the effects of urothelial injury on the deposition and attachment of calcium oxalate crystals is being studied.